Quality Of The Measured Values - Siemens SIMATIC VS120 Operating Instructions Manual

• If these measures still do not lead to success, try the following for example:
• Another remedy is to change the brightness with high contrast in order to clearly detect
4.4

Quality of the measured values

4.4
All the displayed measured values for imaging geometry of a read model are subject to the
following inaccuracies.
Processing precision
• for the position (x and y coordinates): up to ± 0.1 pixels
• for the angle (angle precision): up to ± 0,2°
The processing precision is influenced by the following factors:
• Lighting effects such as reflection and shadow
• Perspective distortion, such when the camera is too close to or at too oblique an angle to
• Differences in the object, for example, dirty objects
• Variation in the trained background structure
Fluctuations in size
Fluctuations in size in the image up to ± 10 % are tolerated, if the specimens are the same
position as the trained pattern. These fluctuations can be caused by the following:
• Different distances between specimens and the lens caused by a different position on the
• Different pattern sizes in the specimen
Perspective distortion
• Perspective distortion in the recorded image are tolerated if the specimens have the
• If there is perspective distortion and the orientation is different, no general statement is
Vision Sensor SIMATIC VS120
Operating Instructions, Edition 02/2006, A5E00757507-01
– Select other lighting
– Specify other more detailed object regions in the ROI
– Enlarge the ROI or similar
the change in the image.
the object
conveyor belt or workpiece holder
same orientation as the trained pattern.
possible. In this case, the shape of the specimens and the angle between the camera
level and pattern level are the factors that determine whether or not the specimens can
be recognized.
Image processing
4.4 Quality of the measured values
4-7